Well I am open to the firmament being a solid. He has a few basic errors.
You can burn in an oxygen free environment if you add an oxidizer to the fuel source. Space is in theory not a complete vacuum assuming what we have been told of space is accurate.
His Disney arc thing is interesting though.
All flying objects though travel in an arc, and it has nothing to do with the firmament. Its due to the force we call gravity pulling us towards the ground.